Design of Passive Optical Network-Based O-RAN X-Haul: A Systematic Approach

The development of high data rate communication technologies have resulted in cell densification, which in turn has led to the development of centralized radio access networks (C-RANs) followed by open radio access networks (O-RANs). The O-RAN segregates the base station into three logical entitities; the central unit (CU), the distributed unit (DU) and the radio unit (RU). The CU, DU and RU require low latency, low jitter and high data rate connections for seamless operation, which is known as X-haul. A passive optical network (PON) is a potential solution for X-haul design. Unfortunately, a PON along with its original uplink protocol is not readily suitable for the purpose. The packetization procedure of PON introduces jitter to the Xhaul bit stream. Further, the delay requirements of the X-haul limit the number of sources that can be connected to the Xhaul. Advanced features like coordinated multipoint requires synchronisation among the different X-haul bit streams as well. Therefore, in this paper, we develop an optimal uplink system that allows PON to be used as an X-haul connection technology. The proposal maximizes the throughput of the PON while conforming to the delay and synchronisation requirements. Moreover, the proposal nullifies the jitter introduced by the PON scheduler. We have performed extensive simulations for verifying our results.